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Housework Kills!

November 6, 2012

by Zuberoa Marcos

Female Komodo dragons live about half as long as their male counterparts because the physically exhaustive nature of housework, such as building huge nests and guarding eggs from predators, leaves them weak.

The Komodo dragon (Varanus komodoensis) is the world’s largest lizard—sometimes reaching ten feet in length! Their formidable body size enables them to serve as top predators. They are able to kill water buffalo, deer, wild boar, and even humans.

Researchers from Australia, Indonesia, and Italy tracked 400 individual Komodo Dragons living in eastern Indonesia for ten years and produced a model of the dragons’ growth rate, published recently in the journal PLoS ONE.

Males and females grow at the same rate and remain the same size until age seven, when they reach sexual maturity. From then on, females start putting all their energy into the chores of motherhood, which makes them grow more slowly and die younger.

Meanwhile, the males’ energy reserves go into growing their bodies larger and larger to give them an edge in competing with other males for females and territory. The researchers found that male Komodo dragons live an average of 60 years, while females average just 32 years.

Professor Tim Jessop from the Department of Zoology at the University of Melbourne and a co-author on the study says that “these sex-based differences seem to be linked to the enormous amounts of energy females invest in producing eggs, as well as building and guarding their nests, a process that can take up to six months, during which they essentially fast, losing a lot of weight and body condition.”

The results could have dramatic consequences for the survival of this endangered species. Conservationists estimate that up to 5,000 individuals remain in the wild, but just 350 are breeding females. Early mortality of females affects fertility rates, making it more difficult to mate, and may be aggravating competition between males over the remaining females. The study could help conservation efforts.

Zuberoa Marcos is a former biologist and current science writer based in Barcelona. She writes articles regularly for Science Today.

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